Multitone detector using an adaptive IIR filter

(19)

(11)

EP 0 795 986 A3

(12)	EUROPEAN PATENT APPLICATION

(88)	Date of publication A3:
	22.11.2000 Bulletin 2000/47

(43)	Date of publication A2:
	17.09.1997 Bulletin 1997/38

(21)	Application number: 97301456.6

(22)	Date of filing: 04.03.1997

(51)	International Patent Classification (IPC)⁷: H04L 27/30, H03H 21/00

(84)	Designated Contracting States:
	DE FR GB

(30)

Priority:

11.03.1996 US 615547

(71)	Applicant: LUCENT TECHNOLOGIES INC.
	Murray Hill, New Jersey 07974-0636 (US)

(72)	Inventors:
	Chesir, Aaron Michael Edison, New Jersey 08817 (US) May, Carl Jerome Holmdel, New Jersey 07733 (US)

(74)	Representative: Buckley, Christopher Simon Thirsk et al
	Lucent Technologies (UK) Ltd, 5 Mornington Road Woodford Green, Essex IG8 0TU Woodford Green, Essex IG8 0TU (GB)

(54)	Multitone detector using an adaptive IIR filter

(57) An adaptive Infinite Impulse Response (IIR) filter is provided that can adaptively detect the presence of one or more tones in its input stream. The tones to be detected may be of arbitrary frequency, subject only to a limitation that such tones fall within a frequency band consistent with accepted sampling principles (e.g., a maximum frequency of interest no greater than one-half the sampling frequency -- Nyquist sampling criteria). An IIR filter developed according to the method of the invention will adaptively locate the frequencies of tones to be detected, thereby allowing for frequency drift from nominal expected frequency values with no loss in accuracy. Such a filter will also process the input signal sample-by-sample, thereby avoiding the blocking problem of FFT-based filter approaches. With the filter of the invention, an application can identify the frequencies, associated power levels, SNR and duration of the tones. Thus, such an application can use a simple user specified library of tone parameters to decide if tones of interest are present in the input stream.

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